Due to the trend of developing miniaturized, lightweight and multi-functional electronic products, 3D designs of electronic elements and circuits have now become inevitable. By way of designing 3D circuit structures, complicate circuits can be realized within a further limited space and electronic products can be further reduced in volume without adversely affecting their intended functions.
Currently, the frequently adopted techniques for fabricating 3D circuits include double-injection molding, laser direct structuring, in-mold decoration injection molding, 3D photo imaging, hot embossing, capture decal and so on. Among others, laser direct structuring is the most common technique for forming a 3D circuit structure, but it has the disadvantages of relatively high cost. On the other hand, the in-mold decoration injection molding frequently has the problems of ink washout, deformed film, poor adhesion between the hot melt plastic and film.
However, with respect to the currently available 3D circuits, no matter how they are fabricated, they all have metal conducting traces formed on the surfaces of a carrier. Further, the exterior of the carrier is not protected by any means and the metal conducting traces formed thereon are exposed to an open space. Therefore, the conventional 3D circuits are easily subjected to moisture, dust and scratch when they are touched or undergoing subsequent fabrication processes. Besides, the metal conducting traces have poor adhesion to the surfaces of the carrier and tend to peel off when they are touched or undergoing subsequent fabrication processes, which will adversely affect the electrical characteristics of the 3D circuit structure in use. Further, since the metal conducting traces are exposed to the open space, the circuit trace layout of the conventional 3D circuit is not secure for use and fails to comply with relevant safety codes of electrical insulation.
It is therefore tried by the inventor to develop a 3D circuit structure that is waterproof, dustproof, scratch-resistant, peeling-proof, secure for use, and compliant with safety codes of electrical insulation, enabling the 3D circuit structure in use to have stable electrical characteristics.